The fluidized-bed technique is a widely used method in chemical technology and is employed predominantly in drying processes. Fluidized-bed reactors are also encountered in fermentation technology, for example in the form of bubble columns. The antibiotic Patulin, for example, can be produced in high yields in such a reactor by means of immobilized Penicillium urticae [Berk et al., Can. J. Chem. Eng. 62, 120 (1984)].
Fluidized-bed reactors have also proven suitable in enzyme technology, in particular when immobilized enzymes are used. By means of this technology, it was possible to increase substantially the stability and hence the spacetime yield of certain enzymes, and this led therefore also to industrial application. If liquids were used in these systems, they have hitherto been composed of only one phase, predominantly aqueous solutions. In this respect, it was only possible to use such a system for substrates which are largely water-soluble.
Particularly in enzyme technology, however, it is desirable also to be able to use water-insoluble compounds as substrates. A correspondig system has hitherto been accomplished only in stirred reactors. The enzyme is then in the aqueous phase and the substrate is in an organic phase which is immiscible with water. The two phases are intimately mixed by means of stirring, so that the enzyme can reach its substrate in the form of fine droplets. This system has hitherto not been transferable to fluidized-bed reactors, because the problem of segregation of the aqueous and organic phases had not been solved. Immobolized biocatalysts can admittedly also be used in stirred reactors, but more extensive wear of the immobilized system than in the case of a fluidized-bed reactor was then observed due to increased attrition.
In order to be able to exploit the advantages of the fluidized-bed reactor also for reactions with biocatalysts in two-phase liquid systems, an appropriate device has been provided wherein, surprisingly, the feared segregation of the two liquid phases is no longer a problem.